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import NNG.Metadata
import NNG.MyNat.Addition
import Std.Tactic.RCases
import Mathlib.Tactic.LeftRight
Game "NNG"
World "AdvProposition"
Level 7
Title ""
open MyNat
Introduction
"
Statement or_symm
""
(P Q : Prop) : P ∨ Q → Q ∨ P := by
intro h
rcases h with p | q
right
exact p
left
exact q
Conclusion